Where they are Put your hands on your back, beside your spine at about waist level—voila!

What they do Your kidneys are like your body’s janitors. Without them we’d be swimming in our own waste. Job One for the kidneys is to filter waste products out of the blood, including the byproducts of most HIV meds in the nucleoside or “nuke” class, such as tenofovir (Viread) and emtricitabine (Emtriva). Your body dumps these wastes when you urinate.

Interesting kidney fact We’re born with a pair, yet we can manage with just one. That’s why you can donate a kidney and remain alive and well.

How they multitask Your kidneys also help build blood and bones. They produce vital chemicals, including: erythropoetin, which stimulates red blood cells to grow; calcitriol, an active form of vitamin D needed for healthy bones; and hormones that control blood pressure.

How to keep them chugging Many people have kidneys that function at less than 100 percent. That may be OK, but for some it can still lead to kidney disease. A few simple tests will detect any signs of trouble.